1. Field of the Invention
The present invention relates to an anti-adhesive agent for asphalt mixtures, which has a strong anti-adhesive effect and a strong release effect on asphalt mixtures, and which does not readily separate at ordinary temperatures or low temperatures, even after dilution with water.
2. Description of Related Art
Asphalt mixtures, which are used for road paving, comprise asphalt, which is an adhesive, and aggregates, which constitute the foundation for the road. The asphalt is heated to a liquid state and mixed with the aggregates, then cooled and solidified, which gives rise to adhesive properties.
It is important to prevent the asphalt mixtures from adhering to devices and equipment, so as to avoid productivity losses in asphalt mixing plants and in road paving sites where the asphalt mixtures are handled. In particular, if the asphalt mixture adheres to the equipment in asphalt mixing plants, such as hoppers, skip conveyors and belt conveyors, the asphalt mixture will gradually build up in places where it adheres, resulting in blockages and the like, which greatly reduce work efficiency.
Consequently, anti-adhesive agents for asphalt mixtures having an anti-adhesive effect and a release effect are necessary in order to prevent adhesion and buildup of the asphalt mixtures on these hoppers, skip conveyors and belt conveyors.
Conventionally, in order to release asphalt mixture that has adhered to hoppers, skip conveyors and belt conveyors, mineral oils such as light oils and heavy oils are regularly dispersed on the hoppers, skip conveyors and belt conveyors from tanks, by way of piping lines.
There have, however, been concerns about methods using light oils and heavy oils, in terms of the impact on the environment due to the outflow of the light oils and heavy oils that are atomized. Thus, there have been numerous reports of anti-adhesive agents for asphalt mixtures with performances equal to or better than those of light oils or heavy oils, which can thus reduce the usage of the same, and which can be used diluted with water.
Patent Literature 1 discloses an emulsion-type anti-adhesive agent for asphalt mixtures, in which animal and vegetable oils and a fatty acid ester of polyoxyethylene sorbitol are diluted and emulsified in water. However, with this anti-adhesive agent, there were problems that large amounts of animal and vegetable oils must be admixed in order to achieve a good result, and after dilution in water, oil/water separation occurs in the tank with the passage of time, which tends to result in a concentration gradient in the tank, such that a stable anti-adhesive effect and release effect cannot be achieved.
As a means for solving the problem of oil/water separation over time, methods have been proposed in which base materials with high affinity for water, and which do not contain oily components, are used; Patent Literature 2 discloses an anti-adhesive agent for asphalt mixtures using a polyhydric alcohol, while Patent Literature 3 discloses an anti-adhesive agent for asphalt mixtures using a polyoxyalkylene glycol derivative.
However, while these anti-adhesive agents had good stability after dilution in water and were capable of producing a stable anti-adhesive effect, their release effect was insufficient, and in particular the performance was not sufficient for use on plant equipment such as hoppers and skip conveyors to which asphalt mixtures readily adhere.
Furthermore, Patent Literature 4 discloses an emulsion type anti-adhesive agent for asphalt mixtures in which a terpene compound serving as an oily component and a non-ionic surfactant or an anionic surfactant are used. However, with this anti-adhesive agent as well, large amounts of the terpene compound are blended in order to achieve a good release effect, while the stability after dilution with water is insufficient, such that it is not possible to arrive at a stable anti-adhesive effect and release effect.
Accordingly, the current situation is that it has not been possible to produce an anti-adhesive agent for asphalt mixtures with which the water-diluted solution does not readily separate, and which exhibits a stable anti-adhesive effect and release effect.